Semiconductors MCQ Practice Test

Q1. A p-type semiconductor is created by doping a semiconductor material with which of the following impurities?

• A. Phosphorus
• B. Arsenic
• C. Boron ✓
• D. Aluminum

Q2. What is the primary function of the n-type region in a p-n junction diode?

• A. To provide a source of majority carriers (electrons). ✓
• B. To increase the reverse bias voltage.
• C. To reduce the forward bias current.
• D. To decrease the depletion width.

Q3. What is the primary function of the n-type dopant in a silicon wafer during the fabrication of a metal-oxide-semiconductor field-effect transistor (MOSFET)?

• A. To create a p-type region
• B. To increase the bandgap energy of the semiconductor
• C. To introduce donor impurities and increase electron concentration ✓
• D. To reduce the carrier mobility of the semiconductor

Q4. A PN junction diode is forward-biased when the p-side is connected to a voltage source with respect to the n-side, and the voltage is greater than the built-in potential barrier. What is the approximate value of the built-in potential barrier for a silicon PN junction diode?

• A. 0.2 V
• B. 0.5 V
• C. 0.7 V ✓
• D. 1.2 V

Q5. A semiconductor device is fabricated using a process that involves implanting boron ions into a silicon wafer. What is the primary purpose of this ion implantation step?

• A. To create a p-type region with a high concentration of holes ✓
• B. To create a n-type region with a high concentration of electrons
• C. To create a region with a high concentration of impurities
• D. To create a region with a high concentration of defects

Q6. A silicon wafer is doped with boron to create a p-type semiconductor. What is the effect of the boron doping on the silicon crystal lattice?

• A. The boron atoms replace some of the silicon atoms in the crystal lattice, resulting in a lack of electrons. ✓
• B. The boron atoms occupy interstitial sites within the crystal lattice, causing the lattice to expand.
• C. The boron atoms create additional holes in the valence band, allowing for easier current flow.
• D. The boron atoms introduce impurity levels in the forbidden gap, affecting the semiconductor's energy band structure.

Q7. A MOSFET is classified as a type of “depletion” mode device when its threshold voltage is < 0 V.

• A. reverse biased
• B. forward biased
• C. depletion mode ✓
• D. enhancement mode

Q8. In a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor), what is the primary function of the gate oxide layer?

• A. It acts as a conductor to allow current to flow between the source and drain
• B. It provides mechanical support to the gate electrode
• C. It isolates the gate electrode from the substrate and source/drain regions, allowing for high voltage resistance ✓
• D. It enhances the mobility of charge carriers in the channel region

Q9. A MOSFET is in saturation region when:

• A. The gate-source voltage is less than the threshold voltage.
• B. The drain-source voltage is less than the gate-source voltage minus the threshold voltage.
• C. The drain-source voltage is greater than the gate-source voltage minus the threshold voltage. ✓
• D. The channel is fully depleted of majority carriers.

Q10. A semiconductor material with a bandgap of 1.1 eV is doped with an acceptor impurity. What is the expected effect on the Fermi level?

• A. The Fermi level moves closer to the valence band. ✓
• B. The Fermi level moves closer to the conduction band.
• C. The Fermi level remains unchanged.
• D. The Fermi level moves to the middle of the bandgap.

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